Experiences form the deconstruction of the Bridge Altstadter Bahnhof in the city of Brandenburg - Part 1: Investigation and findings on the announcement behavior of large-format tendons with pre-stressing steel susceptible to stress corrosion cracking

The bridge "Altstadter Bahnhof" in the city of Brandenburg a. d. Havel was a large pre-stressed concrete structure that provided an elementary traffic junction. In contrast to common pre-stressed concrete structures with small tendons, large-format pre-stressing tendons were used in the longitudinal direction for the main superstructure. In the case of the present bridge, the tendon consisted of 392 oval strands made in the steel mill of Hennigsdorf, Germany, which are considered to be susceptible to stress induced corrosion cracking. During structural investigations, a high degree of embrittlement of the prestressing steel was detected, so that the bridge had to be demolished on May 19, 2021. Previously, in the area of detected prestressing strand breaks, longitudinal cracks appeared in the webs instead of the usual bending cracks. The different damage indication in the case of prestressing steel prompted the Federal Ministery of Transport to initiate further investigations. In cooperation with the Landesbetrieb Strassenwesen Brandenburg, the Hochschule fur Technik und Wirtschaft Dresden and the Bundesanstalt fur Materialforschung und -prufung (BAM), experimental investigations were designed and carried out on site. Specifically, targeted damage to the large-format tendon was carried out at two measuring points in order to reproduce and validate the damage pattern previously found. The concept, results from the investigations and findings for similar structures are the subject of the following first article (Part 1). The following part 2 will focus on the measurement methods and monitoring systems used during the experiments.